First determination of the spin-parity of ${\Xi }_c(3055{)}^{+,0}$ baryons

Abstract

The ${\Xi }_b^{0(-)}\to {\Xi }_c(3055{)}^{+(0)}(\to D^{+(0)}\Lambda ){\pi }^{-}$ decay chains are observed, and the spin-parity of ${\Xi }_c(3055{)}^{+(0)}$ baryons is determined for the first time. The measurement is performed using proton-proton collision data at a center-of-mass energy of $\sqrt{s}=13\text{TeV}$, corresponding to an integrated luminosity of $5.4{\text{fb}}^{-1}$, recorded by the~$\text{LHCb}$ experiment between 2016 and 2018. The spin-parity of the ${\Xi }_c(3055{)}^{+(0)}$ baryons is determined to be $3/2^{+}$ with a significance of more than $6.5\sigma$ ($3.5\sigma$) compared to all other tested hypotheses. The up-down asymmetries of the ${\Xi }_b^{0(-)}\to {\Xi }_c(3055{)}^{+(0)}{\pi }^{-}$ transitions are measured to be $-0.92\pm 0.10\pm 0.05$ ($-0.92\pm 0.16\pm 0.22$), consistent with maximal parity violation, where the first uncertainty is statistical and the second is systematic. These results support the hypothesis that the ${\Xi }_c(3055{)}^{+(0)}$ baryons correspond to the first $D$-wave $\lambda$-mode excitation of the ${\Xi }_c$ flavor triplet.

arXiv commentAll figures and tables, along with any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/1603 (LHCb public pages)

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